1. Field of Invention
The invention relates to a method of manufacturing a hollow micro-needle structure, and more particularly to a method of manufacturing a hollow micro-needle structure using a photoresist layer in conjunction with two mask layers.
2. Related Art
At present, a hollow micro-needle array has been adopted to get a blood sample or get a minor fluid sample in the medical technology, may be applied to an injection or a drug delivery patch in the biotechnological applications, or may be used as micro electrodes in the opto-electronic industry. The hollow micro-needle array may be manufactured using various materials, such as a semiconductor material, a polymeric material or a metal material. When the hollow micro-needle array is manufactured by the semiconductor material, the hollow micro-needle array has to be frequently formed on a silicon wafer. The conventional process of manufacturing the hollow micro-needle array by the semiconductor material needs a lot of dry-etching steps, a lot of wet-etching steps and a lot of film depositing steps. Thus, the manufacturing procedures are complicated and time consuming, and the yield is low and the manufacturing cost is high.
The hollow micro-needle manufactured by the conventional manufacturing processes usually has a ball-shaped end having the poor jabbing function. Furthermore, the root end of the air passage in the micro-needle is usually greater than the distal end, thereby limiting the fluid flowing through the micro-needle. In order to keep the size of the inner air passage constant and maintain the intensity of the micro-needle, the density of the micro-needles in the micro-needle array cannot be easily increased. Thus, the fluid sample amount obtained through the micro-needle array and the delivered fluid are often insufficient. The smaller inner air passage also increases the flowing resistance of the fluid. Thus, a larger driving force has to be provided at the root end of the micro-needle, and this also increases the cost of the apparatus using the micro-needle array.
U.S. Patent Publication No. 2005/0011858 provides a micro-needle array and a method for fabricating the hollow micro-needle array, wherein a mold for a tip end portion of the micro-needle is formed according to the anisotropic property of wet-etching, and then the inner air passage of the micro-needle is defined using the patterned photoresist. Thereafter, a metal layer is deposited on the patterned photoresist. Finally, a de-molding procedure and a dry-etching procedure are performed to form the micro-needle. In this patent, the number of manufacturing steps and the number of kinds of manufacturing processes are also very great, which is not advantageous to the decrease of the manufacturing cost. In addition, no hole can be formed on the sidewall of the micro-needle using the technology of the '858 patent.
U.S. Patent Publication No. 2003/0009113 provides micro-needles and methods of manufacture and use thereof. The micro-needles are formed by way of plastic injection molding. Thus, the mold has to be very precise and the de-molding angle has to be designed very precisely. The micro-needles are only suitable for the mass production. In addition, no hole can be formed on the sidewall of the micro-needle using the technology of the '113 patent.
Thus, it is an important subject of the invention to provide a method of manufacturing a micro-needle structure in a simple manner.